Table 2. Descriptive Statistics for Detection Frequencies (DF, %) and Concentrations (pg/m³ for Air Particles; μg/L for Runoff Water; and ng/g for Roadside Soils) of PPDs and PPD-Qs in Hong Kong.

	air particles (n = 16)			runoff water (n = 9)			roadside soils (n = 12)
compounds	DF	median	range	DF	median	range	DF	median	range
IPPD	100	0.91	0.44–2.73	94	0.01	<IDL–0.21	96	1.13	0.66–24.5
DPPD	81	0.50	<IDL–0.70	56	0.01	0.01–0.02	100	11.8	3.63–84.4
CPPD	75	0.38	<IDL–0.74	100	0.01	<IDL–0.05	92	1.19	0.73–15.4
6PPD	100	1.78	0.82–6.30	100	0.32	0.21–2.71	100	309	31.4–831
DTPD	56	2.86	<IDL–2.88	56	0.01	<IDL–0.01	72	4.82	<IDL–6.78
total PPDs		6.07	1.75–9.41		0.24	0.04–3.00		381	36.3–847
IPPD-Q	94	0.82	<IDL–86.36	100	0.56	0.18–0.95	60	3.06	<IDL–564
DPPD-Q	100	1.91	0.93–95.7	100	0.19	0.11–0.35	100	60.2	2.87–747
CPPD-Q	69	0.17	<IDL–17.5	94	0.06	<IDL–0.31	72	3.12	<IDL–152
6PPD-Q	100	1.18	0.54–13.8	100	1.12	0.21–2.43	100	234	9.50–936
DTPD-Q	63	0.13	<IDL–7.96	50	0.02	0.01–0.82	92	7.94	1.94–107
total PPD-Qs		4.92	2.52–196		2.17	0.74–3.87		395	12.4–1976